This invention relates to a cooling device to cool materials by circulating cold air with a cooling fan and also relates to a method of cooling with the device. Specifically, this invention relates to a cooling device used for freeze-storing foodstuff, a cooling device that cools materials during the conveyance, and a method of cooling with the cooling device.
In cooling devices such as freezers, a forced cold air circulating system is used for cooling. Air cooled by a cooling coil is forced to circulate by a cooling fan in a cooling chamber. Therefore, the cooling chamber has less inner temperature irregularity and cooling time is decreased.
For example, in a conventional freezer, a partition divides the inner space into a cooling coil part having a cooling coil such as a fin-tube type and a cooling fan, and a freezing chamber for freeze-storing foodstuff. The cooling coil is connected with a compressor, a condenser, or the like. A refrigerant circulates in these elements and evaporates in the cooling coil.
To circulate cold air between the freezing chamber and the cooling coil part, a ventilation port and a suction port are provided. The ventilation port discharges cold air from the cooling coil into the freezing chamber while the suction port sucks cold air of the freezing chamber into the cooling coil.
Air cooled by the cooling coil is discharged into the freezing chamber by the cooling fan via the ventilation port. Foodstuffs inside the freezing chamber are cooled with the cold air flowing in the freezing chamber. The air heated by heat exchange with the foodstuffs is sucked by the suction port into the cooling coil part, cooled again by the cooling coil, and ventilated into the freezing chamber.
An example of conventional cooling devices to cool food in the conveyance by means of this cooling method is mentioned more specifically in the following. Cooling devices that cool food during the conveyance include spiral freezers, tunnel freezers, or the like. A spiral freezer cools food on a belt moving spirally by a rotating drum in a thermal insulating box. A tunnel freezer cools food on a belt moving horizontally in a thermal insulating box.
FIG. 11 shows a cross section in a horizontal direction of a conventional spiral freezer. A thermal insulating box 21 is formed by filling a thermal insulator 23 between metal plates 22. A food inlet 24 and a food outlet 25 are formed in the thermal insulating box 21. A belt-driving plate 28 is attached spirally to the outer periphery of a rotating drum 27 that rotates around a shaft 26 (FIG. 12). A belt 29 is mounted on the belt-driving plate 28.
A food delivery belt 30 is provided to the food outlet 25. The rotating drum 27 integrated with the belt-driving plate 28 is placed in a tubular drum case 31. A cooling unit case 32 is connected to the drum case 31.
Inside the cooling unit case 32, a cooling coil 33, cooling fans 34, an air course 35 for discharging cold air, and an air course 36 for sucking cold air are formed. Typically, the cooling coil 33 is a fin-tube.
FIG. 12 shows a cross-section in the vertical direction of the conventional spiral freezer shown in FIG. 11. A rotating drum 27 is disposed inside the drum case 31 with an attachment column (not shown) in order to rotate around the shaft 26.
FIG. 13 shows a cross section taken along a line Ixe2x80x94I of FIG. 11. In FIG. 13, the cross-section along the line Ixe2x80x94I is overlapped with a cross section comprising the food inlet 24 part and the food outlet 25 part in order to clarify the condition of the food conveyance. The cooling coil 33 is connected with a compressor, a condenser, etc (not shown). A refrigerant circulates in these elements, and evaporates in the cooling coil 33.
A process for cooling food is explained below by referring mainly to FIG. 11. First, a foodstuff is delivered into the thermal insulating box 21 from the food inlet 24. The foodstuff is mounted on the belt 29 and moves in a direction indicated by an arrow xe2x80x98axe2x80x99. The belt 29 is shaped like a ring as. a whole and mounted by being combined with the belt-driving plate 28.
As shown in FIG. 13, when the food conveying drum 27 rotates, the belt 29 moves upward along the surface of the spirally-shaped belt-driving plate 28 due to an extruding force created by the rotation of the belt-driving plate 28 integrated with the food conveying drum 27, and also by a drawing force of the belt 29 provided by a separate driving power source. As the belt 29 is shaped like a ring, it circulates on the belt-driving plate 28. A foodstuff 38, which reaches the top step of the belt-driving plate 28 due to the moving belt 29, continues to move in a direction indicated by an arrow xe2x80x98bxe2x80x99 to the food outlet 25, and delivered with a food delivery belt 30 out of the thermal insulating box 21. In this process of the upward move of the foodstuff 38 at the food conveying drum 27, the foodstuff 38 is cooled.
As shown in FIG. 11, cold air from the cooling coil 33 is discharged by the cooling fans 34 in a direction indicated by arrows labeled xe2x80x98cxe2x80x99. The cold air then passes through an air course 35 for discharging cold air and discharged into the drum case 31. Cold air in the drum case 31 moves up the respective steps of the belt-driving plate 28 along the inner wall of the drum case 31 so that the foodstuff on the belt 29 is cooled. The foodstuff 38 is cooled continuously while it moves from the bottom step to the top step of the belt-driving plate 28, and thus cooling is completed by the time the food reaches the top step.
In the drum case 31, the cold air is heated by heat exchange with the foodstuff and returns to the cooling coil 33 through a cold air suction part 36. The returning air is cooled again by the cooling coil 33 and discharged by means of the cooling fans 34 in the direction indicated by the arrows labeled xe2x80x98cxe2x80x99.
To ventilate cold air uniformly from the bottom to the top steps of the belt-driving plate 28, the height of the cooling coil 33 is adjusted to be substantially equal to the height from the bottom to the top step of the belt-driving plate 28, and a plurality of cooling fans 34 are arranged to substantially cover the entire surface of the front of the cooling coil 33 as shown in FIG. 12.
FIG. 14 shows a vertical cross-section in the longitudinal direction of a conventional tunnel freezer. A thermal insulating box 39 is formed by filling a thermal insulator 40 between metal plates 41. In the upper portion of the thermal insulating box 39, a plurality of cooling coils 42 are aligned in the longitudinal direction.
At the rear of respective cooling coils, cooling fans 43 are arranged. A continuous belt 44 for conveying foodstuffs circulates by moving horizontally in the thermal insulating box 39. Additionally, a food inlet 45 and a food outlet 46 are formed in the thermal insulating box 39.
First, when foodstuff is mounted on the belt 44 at the front of the food inlet 45, the foodstuff passes the food inlet 45 together with the moving belt 44 and moves in the thermal insulating box 39 in a direction indicated by an arrow xe2x80x98dxe2x80x99. Cold air discharged from the cooling coil 42 in a direction indicated by an arrow xe2x80x98exe2x80x99 by the cooling fans 43 moves in the directions indicated by arrows xe2x80x98fxe2x80x99, xe2x80x98dxe2x80x99, and xe2x80x98gxe2x80x99, and returns to the rear of the cooling fans 43. The returning air passes through the respective cooling coils 42 sequentially to be discharged again in the xe2x80x98exe2x80x99 direction. By means of such a circulation of cold air, foodstuffs on the belt 44 are cooled while being moved in the xe2x80x98dxe2x80x99 direction.
The above explanation is about an example of conventional cooling devices. In such cooling devices, the temperature of air returning to a cooling coil increases due to heat exchange with foodstuff, and the air contains vapor generated from the foodstuffs. When the returning air is cooled again by the cooling coil, moisture in the returning air will be frosted and will adhere to the cooling coil.
Because a large amount of frost deposited on the cooling coil deteriorates the cooling performance, defrosting is carried out by using a separate defrosting heater. However, this method of defrosting may involve manual operation. Cooling operation must be stopped at defrosting, so this will deteriorate cooling efficiency. Lowering efficiency has been a problem in cooling a large amount of food.
In such a conventional spiral freezer, heat exchange is carried out by passing air through a cooling coil. Therefore, it requires an air course to introduce returning cold air to the rear of the cooling coil and also an air course to introduce discharged air into a drum case. As a result, a certain space for the air courses should be provided in the front and the rear of the cooling coil in addition to a space for housing the cooling unit. Thus, the device inevitably becomes large.
When a large cooling coil is provided to improve the cooling performance, the entire device will increase in size. Therefore, space-saving has been difficult to accomplish, especially for a device for rapid cooling.
In a conventional tunnel freezer as mentioned above, cooling units are aligned along the longitudinal direction of the belt. Therefore, when the number of the cooling units is increased for improving the cooling performance, the device will be extended in the longitudinal direction by the number of the increased cooling units. As a result, it has been difficult to save space in a tunnel-freezer, especially one for rapid cooling.
To solve the problems in the conventional methods, embodiments of the present invention provides a cooling device that can decrease frost deposits on a cooling coil by solidifying vapor in cold air before the air returns into the cooling coil in order to omit the necessity of defrosting in a steady state. The present invention also provides a cooling method using the device. Embodiments of the invention also provide a cooling device that enables rapid cooling with a smaller space and reduces frost deposited on the cooling coil, and also a cooling method using the device.
A first cooling device in accordance with one embodiment of this invention comprises a thermal insulating box, a cooling coil part of a cooling coil disposed on at least one inner wall of the thermal insulating box, a fan arranged in front of the cooling coil part, and a cooling chamber as a space in front of the fan. The fan discharges air into the cooling chamber to flow therein. In the cooling device, dry-cooling air present in the cooling coil part is sucked from the rear of the fan and discharged into the cooling chamber. An air volume corresponding to the volume of sucked air passed through the cooling coil part is fed from the cooling chamber to the cooling coil part through areas not occupied by the cooling fan. The air feeding speed is set so as to permit vapor generated in the cooling chamber to solidify until the vapor (moisture) is brought into contact with the surface of the cooling coil.
In such a cooling device, most of the cold air in the cooling chamber circulates in the same cooling chamber without returning to the inside of the cooling coil, so that most vapor generated in the cooling chamber will solidify in the cooling chamber. Furthermore, cold air returning to the inside of the cooling coil is also cooled in front of the cooling coil before it makes contact with the same coil, and thus, most vapor in the returning cold air will solidify. Therefore, absolute volume of the vapor included in the cold air returning to the cooling coil is subtle in volume, and it is removed further before the cooled air returns to the cooling coil. As a result, amount of frost deposited on the cooling coil can be considerably reduced.
Preferably in the cooling device, the speed for the vapor to solidify before a contact with the cooling coil surface (wind speed) is more than 0 m/min. but not more than 5 m/min.
Accordingly, most of the vapor can solidify by cooling cold air before returning into the cooling coil.
Preferably, a speed for the vapor to solidify before a contact with the cooling coil surface (wind speed) is from 0.5 m/min. to 3.5 m/min. Accordingly, most of the vapor can solidify by cooling cold air before the air returns into the cooling coil.
Preferably, the speed of airflow sucked from the cooling coil is greater than the speed of airflow fed to the cooling coil part. Accordingly, most of the vapor can solidify by cooling cold air fed to the cooling coil before the air returns into the cooling coil.
Preferably, the area of airflow sucked from the cooling coil part is smaller than that of airflow fed to the same cooling coil part. Accordingly, the speed of the cold airflow fed to the cooling coil part can be reduced.
Preferably, a plurality of the cooling fans are arranged in front of the cooling coil, and the respective cooling fans are attached in an inclined state to the cooling coil so that cold air discharged from the cooling fans will intersect. Accordingly, cold air can be concentrated on a material to be cooled, and it is further advantageous for rapid cooling.
Preferably, a clearance is formed between the rear of the cooling coil and the inner wall of the chamber. Accordingly, the sucked air can be easily introduced to the rear of the fans.
Preferably, the clearance ranges from 20 to 50 mm. Accordingly, the cold air can be prevented from diffusing in the clearance, and sufficient volume of cold air can be flown.
Preferably, the cooling device is selected from the group consisting of a refrigerator, a freezer, a refrigeration device, a refrigeration device for a automatic vending machine, a cold storage, a cool-keeping car, and a freezer car.
Preferably, the refrigerator and the freezer are for intended home use.
Preferably in the respective cooling devices, input of heaters is not necessary to defrost the cooling coil in a steady state. Accordingly, cooling efficiency can be improved since the temperature in the cooling chamber will not be raised due to heating with a heater.
Preferably, the cooling device further comprises a partition to divide the inside of the thermal insulating box into a cooling space and an inner wall side space positioned outside this cooling space, and a ventilating hole to flow air between the cooling space and the inner wall side space, in which the cooling coil is arranged with its rear facing the inner wall side space, with its side being adjacent to the inner wall and the front being incorporated into the inner periphery of an opening formed at the partition. In the device, cooling fans are arranged in front of the cooling coil, and the cooling fans are set to rotate in the direction to discharge air behind the fans directly toward the same fans.
Accordingly, most of the cold air in the cooling chamber will circulate in the cooling chamber without returning to the cooling coil inside. Therefore, most of the vapor generated in the cooling chamber solidifies in the cooling chamber, and the amount of frost depositing on the cooling coil can be decreased. Moreover, it is not necessary to provide any special spaces for an air course to circulate cold air in the front or the rear of the cooling coil, and thus it can save space.
Preferably in the cooling device, cold air discharged from the cooling fans is reflected by the wall facing the cooling fans in order to return to the cooling fan part. Accordingly, cold air discharged into the cooling space can be returned easily to the cooling coil side.
Preferably, the cooling device further comprises a means to convey a material to be cooled in the cooling space, and the cooling fans are disposed adjacent to the conveying means. Accordingly, cold air can be discharged directly to the material, and rapid cooling can be carried out.
Preferably, the cooling device further comprises a rotating drum arranged in the cooling space and also a belt-driving plate attached spirally to this rotating drum, in which the conveying means is a belt that circulates while moving spirally on the belt-driving plate due to the rotation of the rotating drum. Accordingly, even a cooling device to convey materials spirally can save space and enables rapid cooling and reduces frost deposited on the cooling coils.
Preferably, the cooling device comprises a plurality of rotating drums, and the rotating drums are provided respectively with cooling coils and cooling fans. The adjacent belt-driving plates of rotating drums are positioned spirally in the direction opposite to each other. The belt is bridged from a belt-driving plate to the adjacent belt-driving plate, and the belt circulates while moving on the belt-driving plates of the respective rotating drums by the rotation in the same direction of the rotating drums. Accordingly, the cooling period in the device can be extended, and consequently cooling performance can be improved.
Preferably, the device has even numbers of the rotating drums, and the inlet and the outlet for materials are formed at substantially the same height in the thermal insulating box. Since such a cooling device does not need a belt to lower a lifted material outside the device, the equipment can be simplified.
Preferably, a plurality of the cooling coils and the cooling fans are arranged along the outer periphery of the belt-driving plate. Accordingly, the cooling performance can be improved as well as a space at the outer periphery of the belt-driving plate can be utilized, and the cooling coils will be extended less in the longitudinal direction, and therefore help save space.
Preferably, the cooling coils are disposed at substantially the same height of the bottom to the top steps of the belt-driving plate, and the plural cooling fans are arranged in front of the cooling coil so that the volume of the air ventilated to the respective steps of the belt-driving plate is equalized substantially. Accordingly, the materials are cooled continuously while it is transferred from the lowest to the top steps of the belt-driving plate, and the cooling performance can be improved.
Preferably, a stopper to prevent sliding of the material is provided on the belt. Accordingly, materials can be prevented from sliding off when the belt is frozen.
Preferably in the cooling device, the conveying means is a belt that circulates while moving in the horizontal direction. Accordingly, even a cooling device to convey materials in the horizontal direction can save space, and enables rapid cooling and reduces frost deposited on the cooling coils.
If the conveying means of a cooling device is a circular belt that circulates while moving in the horizontal direction, the cooling coils are disposed preferably at the both sides of the belt. Accordingly, the cooling performance can be improved while the device is extended less in the longitudinal direction, and thus, space-saving and rapid cooling can be realized.
Preferably the respective cooling fans are disposed at both sides of the belt in front of the cooling coil, and the cooling fans face each other with the belt therebetween. Accordingly, cold air will be overlapped in the cooling space, and this is a further advantage for rapid cooling.
Next, a cooling method of the present invention is provided by using a cooling device comprising a thermal insulating box, a cooling coil part of a cooling coil disposed on at least one inner wall of the thermal insulating box, a fan arranged in front of the cooling coil part, and a cooling chamber as a space in front of the fan. In this method, air is discharged by the fans into the cooling chamber and most of the flowing air is discharged again into the cooling chamber without returning into the cooling coil. This method is characterized in that the flowing air is discharged again into the cooling chamber and the flowing air sucked from the cooling coil are joined before they are discharged into the cooling chamber.
In the above-mentioned cooling method, discharged cold airs different in temperature join and exchange heat between them. As a result, cold air directly heading from the cooling space for the rear of the fans is cooled with the other cold air that is sucked directly from the cooling coil, and a predetermined volume of vapor can solidify in the cooling space.
Preferably in the cooling method using the cooling device, an air volume corresponding to the volume of sucked air passed through the cooling coil is fed from the cooling chamber to the cooling coil through areas not occupied by the cooling fans, and the feeding speed is set so as to permit vapor generated in the cooling chamber to solidify by the time the vapor is brought into contact with the surface of the cooling coil.
Accordingly, most of the vapor in the returning cold air solidifies before contacting with the cooling coil, and frost deposited on the cooling coil can be reduced significantly.
In addition, the speed that the vapor solidifies by the time to contact with the cooling coil surface (wind speed) is preferably more than 0 m/min., but not more than 5 m/min. Accordingly, cold air returning to the inside of the cooling coil is cooled before it returns into the cooling coil so that most of the vapor can solidify.
It is also preferable that the speed that the vapor solidifies by the time to contact with the cooling coil surface (wind speed) is from 0.5 m/min. to 3.5 m/min. Accordingly, cold air returning to the inside of the cooling coil is cooled before it returns into the cooling coil so that the most of the vapor can solidify.